Steam producing humidifiers are utilized in many buildings for maintaining the humidity within the building at a desired level. The steam producing cylinders usually comprise an outer casing or container of a plastic material within which there is placed water and at least two electrodes for passing an electric current through the water to heat the same and thereby produce steam. The outer container or cylinder is made of a material which is resistant to the steam and/or hot water and is usually of a polypropylene material. The electrodes are immersed in the water and alternating current is supplied to the electrode. The current travels through the water and produces the heat which then boils the water.
For any given voltage, the amount of current determines the amount of steam produced. Generally, for new cylinders, it is established that approximately 1 pound of steam requires 1/3 of a kilowatt of electrical energy.
A major problem associated with the steam producing cylinders is scaling of the electrodes and other parts. In an attempt to minimize this problem, purging of the containers at regular intervals is recommended and required.
As will be understood, the continuous boiling of the water leaves an increased mineral accumulation in the remaining water. This mineral accumulation increases the conductivity of the water and thus the amount of current flowing. However, this also results in the scaling of the electrodes and in turn, the scaling on the electrodes acts as a insulating layer thus decreasing the efficiency of the steam producing cylinder.
It is well understood that given a certain voltage, the value of the current will change depending on various parameters including the size of the cylinder and/or the amount of the water for a given electrode size. One can also change the conductivity of the water as above mentioned wherein the current will increase in proportion to the water conductivity. One can also vary the space between the electrodes and/or vary the size and thickness of the electrodes.
The source of the water itself will be a factor in the operation of the steam producing cylinder. Thus, the amount of dissolved minerals will vary from one city to another as well as from one well to another. As aforementioned, purging the cylinders is required at frequent levels.
The calcification on electrodes is one problem. Deposits also form on the inner walls of the container and some of the deposits from the electrodes and/or the inner water walls may separate and accumulate on a mesh or screen filter at the bottom of the cylinder. Naturally, blocking the mesh filter will accelerate the rate of deposits due to lack of purging and eventually plug the entire cylinder rendering it inoperable. Furthermore, one may find cylinders which are partially melted due to arcing and some cylinders have been known to catch fire or even explode.
Apart from the straight scaling problem, corrosion is a further problem which eats away at the electrodes. These electrodes are of a ferrous material and are susceptible to arcing between electrodes. This arcing can weaken and destroy the electrodes.
The electrodes themselves are normally of a perforated material which increases the circulation and contact with water that travels through the apertures or pores in the electrode. However, the apertures and pores rapidly become clogged due to scaling and indeed, the small size thereof renders them very susceptible to the same.
For the reasons mentioned above, the steam generating often become inoperable and must be completely discarded. Often, due to the scaling problems, the electrodes damage separators which are used within the cylinders and the cylinders must be discarded.
It has been proposed in the art to help overcome the problem of scaling by coating the electrodes with various materials. While such methods have achieved varying degrees of success, they have not been widely adopted.
Conventional constructions of electrodes seen in the prior art are shown, for example, in U.S. Pat. No. 4,288,684. However, this patent does not teach any recycling of steam generating cylinders.